The short answer: On authentication, the two platforms are equal: neither publishes SPF, DKIM enforcement, or DMARC for your custom domain, so you do the same DNS work on both. They differ in threat protection. Microsoft 365 splits advanced controls (Safe Links, Safe Attachments, impersonation protection) into Defender for Office 365, bundled with Business Premium, while Google folds more into Gmail's base filtering and its higher editions.
Email security is rarely why a business picks one suite over the other, but the differences are real once you look at where each platform leaves work for you. This comparison is neutral. It covers authentication setup, anti-phishing tiers, transport encryption, reporting, and the gaps that remain whichever you choose.
Plans and bundles change frequently. Treat the tier notes below as a map of where to look, and confirm current edition details on each vendor's plan comparison page before buying.
Side-by-Side Comparison
| Area | Google Workspace | Microsoft 365 |
|---|---|---|
| SPF record for your domain | You publish it: include:_spf.google.com |
You publish it: include:spf.protection.outlook.com |
| DKIM for custom domain | Generate key in Admin console, publish one TXT record, start authentication | Publish two CNAMEs, enable signing in Defender portal |
| DKIM selector | google by default (configurable) |
selector1 and selector2 |
| DMARC | You publish it; no setting inside the suite | You publish it; no setting inside the suite |
| Baseline spam and malware filtering | Gmail filtering, all editions | Exchange Online Protection, all Exchange Online plans |
| Rewriting links, detonating attachments | Controls in Gmail safety settings; advanced sandboxing on higher editions | Safe Links and Safe Attachments via Defender for Office 365 |
| Impersonation protection | Settings for spoofing of your domain, employee names, and unauthenticated mail | Anti-phishing policies with user and domain impersonation (fuller set in Defender) |
| MTA-STS and TLS reporting | You host the policy and DNS records | You host the policy and DNS records |
| Sender reputation visibility | Google Postmaster Tools (Gmail traffic only) | Message trace and Defender reports; Outlook.com data via SNDS |
| Admin audit and investigation | Admin console reports, Alert Center, investigation tool on some editions | Defender portal, Threat Explorer on higher tiers, Message trace |
The rest of this post explains the rows that need context.
Authentication: A Tie With Different Mechanics
SPF
Neither platform adds an SPF record to your DNS on its own initiative. You publish one TXT record at the root:
v=spf1 include:_spf.google.com ~all # Google Workspace
v=spf1 include:spf.protection.outlook.com -all # Microsoft 365
The ~all versus -all choice is yours on both and is not a platform difference. See SPF hard fail vs soft fail. If you use both suites during a migration, or add marketing and billing tools, the 10-lookup limit applies equally. See SPF too many DNS lookups.
DKIM
This is where setup feels different.
Google Workspace: In the Admin console go to Apps > Google Workspace > Gmail > Authenticate email, select the domain, generate a record, publish the TXT record, and click Start authentication. One record, one selector, public key stored directly in DNS.
Microsoft 365: Publish two CNAME records that point to keys Microsoft hosts, then enable signing in the Defender portal (Email & collaboration > Policies & rules > Threat policies > Email authentication settings > DKIM). Microsoft handles key rotation using the two selectors. Details are in the Microsoft 365 authentication guide.
Practical consequences:
- Google's single TXT record is simpler to publish, but long 2048-bit keys sometimes need to be split into multiple strings at registrars that limit TXT length.
- Microsoft's CNAME approach means the public key is never pasted into your DNS, so Microsoft can rotate it for you.
- Until DKIM is enabled for your custom domain, neither platform signs with a domain that aligns with your From address, which weakens DMARC. Check with the DKIM checker.
DMARC
No platform publishes DMARC for you, and there is no switch inside either admin console that creates one. It is a TXT record at _dmarc.yourdomain.com, identical on both:
v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com
Neither suite provides a built-in DMARC report dashboard. You need an inbox or a DMARC monitoring tool to read aggregate reports. Platform-specific steps are in the Google Workspace DMARC guide and the Microsoft 365 guide. The staging plan for moving to enforcement is in DMARC policy: none, quarantine, reject.
Threat Protection: Where the Platforms Actually Differ
Microsoft 365
Microsoft layers its protection:
- Exchange Online Protection (EOP): baseline anti-spam, anti-malware, and anti-spoofing for all Exchange Online mailboxes.
- Defender for Office 365 Plan 1: adds Safe Links, Safe Attachments, and richer anti-phishing policies. It is included with Business Premium and sold as an add-on for other plans.
- Defender for Office 365 Plan 2: adds investigation and response tooling, attack simulation, and automated investigation. It is included in E5-level licences.
- Preset security policies: Standard and Strict presets apply Microsoft's recommended settings in one step, which helps small teams that cannot tune dozens of policies.
The upside is depth and control. The downside is that protections vary by licence, and an organisation on a lower plan may believe it has Safe Attachments when it does not.
Google Workspace
Google puts a larger share of protection into Gmail's default filtering and into settings that apply across editions:
- Gmail's machine-learning spam and phishing filtering on all editions.
- Admin settings under Gmail > Safety for spoofing and authentication, for example protection against messages that spoof your domain, spoof employee names, or come from unauthenticated senders.
- Link and attachment protections, with the security sandbox and some advanced controls reserved for higher editions. Confirm which edition includes what on Google's current comparison page.
The upside is that a small business gets most of the protection with little tuning. The downside is less granular policy control than Defender offers, and fewer investigation tools on lower editions.
A fair read
Neither product is clearly "more secure". Microsoft gives security teams more knobs at higher licence cost. Google gives small teams good defaults with fewer controls. A tuned Business Premium tenant and a well-configured Workspace Enterprise domain will both stop most commodity phishing, so the gap that decides outcomes is usually configuration discipline: authentication enforced, MFA on, external forwarding restricted, and admin alerts monitored.
Transport Security: MTA-STS and TLS
Both platforms use opportunistic TLS between mail servers, which an attacker can downgrade. MTA-STS closes that gap for mail sent to your domain by publishing a policy that tells senders to require valid TLS.
- Neither platform hosts that policy for your custom domain. You publish a
_mta-stsTXT record and serve a policy file over HTTPS atmta-sts.yourdomain.com. The MTA-STS generator produces both and the MTA-STS checker tests them. - Google has supported MTA-STS for a long time. Microsoft has been rolling out MTA-STS validation for outbound mail and DANE for SMTP in Exchange Online. Rollout status changes, so check Microsoft's current documentation before relying on either.
- The policy's
mx:lines must match your actual MX hostnames, which differ per platform (see the migration section below).
Visibility and Reporting
Google: Postmaster Tools shows domain reputation, spam rate, and authentication results for mail delivered to Gmail users. It is free and independent of your Workspace licence, but covers Gmail recipients only and needs a minimum volume to show data. Admin console reports, email log search, and Alert Center cover the rest.
Microsoft: The Defender portal provides threat reports, spoof intelligence, and, on higher tiers, Threat Explorer for tracing messages. Message trace is available to every Exchange Online admin. For Outlook.com recipients, Microsoft offers Smart Network Data Services (SNDS) to senders.
Microsoft's tooling is broader for dedicated security staff. Google's Postmaster Tools is the more direct signal for deliverability to Gmail, which matters for bulk senders. See Google and Yahoo bulk sender requirements.
Always Your Responsibility, on Either Platform
- Publish SPF, enable DKIM for the custom domain, and publish DMARC.
- Authenticate every third-party sender (CRM, newsletter tool, helpdesk, billing).
- Move DMARC to enforcement after monitoring.
- Enforce MFA for every account, particularly admins.
- Review auto-forwarding and inbox rules, a common step after account takeover (see business email compromise).
- Publish MTA-STS if you want enforced transport encryption.
The email security score checks items 1 to 3 and 6 for any domain on either platform.
Switching Platforms: What Changes
| Item | Google Workspace | Microsoft 365 |
|---|---|---|
| MX | Google's MX records (check Google's current guidance; a single smtp.google.com record is documented) |
yourdomain-com.mail.protection.outlook.com, priority 0 (copy the exact value from the admin centre) |
| SPF include | _spf.google.com |
spf.protection.outlook.com |
| DKIM | TXT at google._domainkey |
CNAMEs at selector1._domainkey and selector2._domainkey |
MTA-STS mx: entries |
Google hosts | Your tenant's mail.protection.outlook.com host |
Remove the old platform's SPF include once cutover is complete, or the old provider stays authorised to send as you. The full sequence is in the Google Workspace email migration checklist.
Frequently Asked Questions
Is Gmail or Outlook more secure for business email?
Neither is inherently more secure. Both block most commodity spam and phishing. Microsoft offers more granular controls at higher licence tiers; Google offers strong defaults with less tuning. Your configuration of authentication and MFA matters more than the vendor.
Does Microsoft 365 set up DMARC automatically?
No. DMARC is a DNS record you publish yourself. The same is true for Google Workspace. Neither platform creates it, so a new domain on either has no DMARC policy until you add one.
Do I need Defender for Office 365 on Microsoft 365?
Not to send authenticated mail, but you need it for Safe Links, Safe Attachments, and the fuller anti-phishing controls. Business Premium includes it. Other plans can add it separately; check current licensing.
Which platform is easier to set up DKIM on?
Google's flow is one TXT record. Microsoft's is two CNAMEs plus a toggle, which is slightly longer but needs no key pasted into DNS. Both take about 15 minutes of work plus DNS propagation time, and both can be verified afterwards with the free DKIM checker by entering the selector shown in the admin console.
Can I use SPF for Google Workspace and Microsoft 365 at once?
Yes, if both send mail from your domain, include both in one SPF record and watch the 10-lookup limit. Do not publish two separate SPF records.
Next step: run the free email audit to see how your domain is configured today, or use the email security setup service if you want the DNS work handled for you.